Measurement of the top quark mass in the dilepton channel in pp collisions at $\sqrt{s}$=7 TeV


We present a measurement of the top quark mass $m_{\rm top}$ in the dilepton decay channel $t\bar{t}\rightarrow(l^{+}\nu_l b)~(l^{-}\bar{\nu}_l \bar{b})$ in pp collisions at $\sqrt{s}=7$ TeV. The data sample of the measurement corresponds to an integrated luminosity of 2.3 fb-1 collected with the CMS detector at the LHC. Events are selected by requiring two leptons, at least two jets and missing transverse energy. The mass is reconstructed from the kinematic characteristics of the events with a full kinematic analysis. A set of templates is constructed from simulated samples and a likelihood fit is performed to derive the mass. The result yields a measurement of $m_{\rm top}=173.3\pm 1.2({\rm stat.})^{+2.5}_{-2.6} ({\rm syst.})$ GeV/c2.

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The document CMS-PAS-TOP-11-016 published on the CERN document server can be found here. The Tables and Figures from the document are reproduced below. Click on the figures to retrieve the PDF version.




Figure Caption
Top quark mass solutions for the KINb method for the two lepton-jet combinations after smearing the jet energy resolution for one selected event in data. The combination #2 is chosen in this case; the solid red line corresponds to the Gaussian fit used to estimate $m_{\rm KINb}$.
Results of the fit for same (different) flavour dileptons are shown on top (bottom) for events with one (left) or at least two b-tags (right). Also shown are the total background plus signal model and the background-only shape (shaded).
Variation of the likelihood used to extract the top quark mass, in the different event categories and for all channels combined.
(Top) Fitted top quark mass values using the KINb algorithm from simulated pseudo-experiments, including signal and background processes, as a function of the actual top quark mass used in the simulation. A linear fit to the points is also shown. (Bottom) The difference (bias) between the linear fit and the actual reconstructed values from the pseudo-experiments. The bias is shown after calibrating the signal parametrization.
Summary of top quark mass measurements in the dilepton channel. The statistical (total) uncertainty associated to each measurement is represented by a bold (thin) red line. The different measurements are compared to the result of the Tevatron combination using up to 5.8 fb-1 of data. The Tevatron results are taken from arXiv:hep-ex/1107.5255v3.

-- PedroSilva - 23-Feb-2012 -- PietroVischia - 24-Feb-2012

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PDFpdf 163402352376774543.pdf r1 manage 15.7 K 2012-02-23 - 17:35 PedroSilva  
PNGpng 163402352376774543.png r1 manage 17.0 K 2012-02-23 - 18:01 PedroSilva  
PDFpdf MassFitLikelihood_exclusive.pdf r2 r1 manage 18.2 K 2012-02-25 - 14:55 PedroSilva  
PNGpng MassFitLikelihood_exclusive.png r2 r1 manage 22.0 K 2012-02-25 - 14:55 PedroSilva  
PDFpdf MassFitResults_exclusive.pdf r1 manage 31.8 K 2012-02-23 - 17:35 PedroSilva  
PNGpng MassFitResults_exclusive.png r1 manage 64.1 K 2012-02-23 - 17:34 PedroSilva  
PNGpng Table1.png r1 manage 115.2 K 2012-02-23 - 17:58 PedroSilva  
PNGpng Table2.png r2 r1 manage 54.7 K 2012-02-23 - 23:10 PedroSilva  
PDFpdf TopMassCalibrationResults_exclusive_final.pdf r1 manage 15.5 K 2012-02-23 - 17:25 PedroSilva  
PNGpng TopMassCalibrationResults_exclusive_final.png r1 manage 12.9 K 2012-02-23 - 17:25 PedroSilva  
PDFpdf topmass_dileptons2011.pdf r1 manage 14.0 K 2012-02-27 - 22:18 PedroSilva  
PNGpng topmass_dileptons2011.png r1 manage 16.9 K 2012-02-27 - 22:17 PedroSilva  
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Topic revision: r6 - 2012-02-27 - PedroSilva
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